Pulverized fuel burner



July 25, 1933. a v I TENNEY 1,920,117

PULVERIZED FUEL BURNER Filed June 29 1929 5 Sheets-Sheet 1 I I V PULVERIZ E R \NVENTOR w W YMT MMWMM%&%;WI

. July 25, 1933. TENN 1,920,117

PULVERIZED FUEL BURNER Filed June 29, 1929 3 Sheets-Sheet 2 July 25,1933. E. H. TENNEY 1, PULVERIZED F-UEL BURNER Filed June 29, 1929 sSheets-Sheet 5 INVENTOR Patented July 25, 19.33

UNITED sures-PATENT OFFlCE EDW ABD H. TENNEY, 0F WEBSTER GROVES,MISSOURI 'rULvEcaIzEn. Fm BURNER Application men an. 29,

t This invention is primarily a novel pulverized fuel burner, that is, adevice employed as at the entrance toa furnace for delivering forimmediate combustion a stream of pulverized coal or similar fuel insuspension in air received at the burner from a transporting passage orpipe; the invention as illustrated being designed more especially foruse with the so-called unit system wherein the coal is reduced inapulverizer and thence conducted directly to the burner and furnace.

One of the principal objects of the present invention is to provide aseparating action in the burner of such character that the coarserpulverized particles will be effectively separated out from the flowingstream while the finer particles and air are delivered, for example, forimmediate combustion in the furnace. It has been ascertained that inpractice, notwithstanding the efficiency of modern pulverizersa-substantial quantity or percentage of relatively coarse material issupplied or likel to be delivered along with the relatively ne material,either continuously or at intervals during the operation of the plant.To the extent that relatively large fuel particles are passed through toa burner and furnace there are decided disadvantages. These particlesare incapableoftburning completely in the shot period of travel throughthe furnace. The particles that are carried up through the boiler andstack without complete combustion cause a substantial loss of fueleconomy, while the portion that settles intothe ash pit tends to theincrease ofslag formation and consequent trouble and expense in theoperation of thefurnace and boiler.

I am aware that so-called classifiers or separators have been proposed,intended to be used at a point between a pulverizer and a burner forseparating and returning coarser particles. These however have not beenhighly satisfactory, and they are bulky and expensive and causecomplicationin the piping arrangements, as well as producing asubstantial loss of pressure or head in the delivered stream of air andfuel, thus consuming excessive power in transporting thetream from thepulverizer to the furnace.

A particular object of the present invention therefore is to afford aburnerwhich will possess the functions of, first, separat- 1929. SerialNo. 374,641.

ing out the coarse-particles from the stream so that they can becollected, forexam le for return to the pulverizer, and second, e

livering the fine particles with the carrying air so that they can beburned immediately at the delivery in the furnace and under the mostadvantageous conditions. It is believedto be new with this invention topro vide' aburner having means for continuously separating out thecoarser particles from the stream while delivering the finer particleswith air for immediate combustion' inthe furnace.

Other objects of the invention include to make possible, in a furnaceburning pulverized fuel, very high rates of complete combustion, andwithout production of smoke, and yet without the need of supplyingunduly high percentages of excess air; also, to permit the production ofa whirling flame of advantageous character, instantaneous combustion,and of small volume.

Other and further objects and advantages of the-present invention willbe explained in the hereinafter following .description of anillustrative embodiment thereof or will be understood'to those skilledin the subject. To the attainment of such objects and advantages thepresent invention consists in the. novel pulverized fuel burner and thenovel features of operation, combination, ar-

rangement and structure herein illustrated or escribed. 4

In the accompanying drawings 'Fig 1 is a more or less diagrammaticelevation of a classifying burner and cooperating elements, beingsupposedto be viewed from the furnace side.-

Fig. 2, on an enlarged scale, shows the. same elevation view of theburner detached, and partly broken away.

Fig. 3 is a vertical section taken substantially through the center ofthe burner and a portion of the furnace wall, being partly a-rightelevation of the burner shown in Fig. 2.

Fig. 4 is a perspective view of the interior arrangement at that portionof the burner where the separated heavy particles are ejected andrecovery'therefrom of finer particles is effected.

' Fig. 5 shows in elevation a modified form Fig. 6 is a central sectionsimilar to Fig. 3, but showing a modification in respect to theadmission of secondary air.

Fig. 7 is a view similar to Fig. 2, but showing a modification inrespect to the bafiling action in the burner.

Fig. 8 is a modification of the device shown in Fig. 5, in similar view.

Referring first to Fig. 1, facing toward the observer are the burner andassociated elements of the present invention. A suitable motor 13 isshown direct-coupled to a pulverizer indicated at 14. This for examplemay be an impact type pulverizer having a fuel inlet or hopper 15 forcrushed coal at one end and a delivery fan at the other end. A returnpipe 16 from the burner may deliver the ejected heavy particles to thehopper 15 or directly to the pulverizer. At a suitable point, forexample at the fan end of the pulverizer, there may be a damper 17 foradmitting additional air under regula tion. The pulverizer may have atangential delivery tube 18 which may be connccted'by an ample transportpipe 19 extending directly to the entrance passage of the classifyingburner 20. The ejection of coarse particles by way of pipe 16 may becontrolled or stopped by cutting off the pipe by damper or valve 16,which also may be closed when the burner is operated by fuel containingno coarse particles.

The burner or classifier 20 is shown as formed with what may be termed acurved passage or conduit 21 forming a continuation of the entrancepassage of the burner, so that the fuel or material ascending throughthe transport pipe 19 will pass upwardly at high velocity and thenceinto the urner and around into the curved passage, with the results tobe described. The cross sectional shape of the passage may vary, but forconvenience is shown as having, 'a four-sided shape rather thancircular. These passage walls are well illustrated in Fig. 3, and fromFigs. 1, 2 and 3 the preferable arrangement will be seen in which theinside wall 22 is shaped as a hollow frustum of a cone and arrangedflaringly toward the furnace. The passage is provided with a number ofapertures 23 discharging fuel and air inwardly into what may be termedthe central space 24. These apertures 23 are preferably elongated in adirection toward the furnace, since this construction increases thecapacity and efliciency of the burner. The resultof the flared form ofthe wall 22 is that the jets discharged through the apertures or slots23 converge in a direction toward the furnace, facilitating the deliverythrough the opening 12 in the furnace wall 12 to constitute a quickburning flame in the combustion chamber. By a curved passage is intendedany passage extending around or substantially around the central space,and it may be spiral, or helical, and with less or more than a singleturn, so long as the travel is along the passage and therefore aroundthe central space. It will be noted that in the illustrated embodimentthe curved passage 21 is in the form of an annular chamber, and theinner wall 22 of the chamber defines an axial passage 24. The openings23 in this inner wall establish communication between the chamber andthe axial passage. The fan and pulverizer l4 deliver air and pulverizedfuel tangentially to the chamber through its outer wall.

The classifying or separating action within the passage 21 takes placeby centrifugal force, tending to throw out to the peripheral or outsidewall 25 the coarse and heavy particles, while the finer particles, beinglight enough to move along with the air flow are carried through thesystem of discharge apertures or slots 23 into the central space 24. Thedifferentiation between material thrown outwardly and material drawninwardly may of course be varied'by altering the character of thepassage, the velocity of travel, etc. For pulverized fuel combustion, itis preferable to discharge into the central space only the very finefuel particles, allowing all coarse and heavy particles to pass alongthe periphery to ejection. The finer particles discharged with airthrough the inside Wall apertures are referably directed at an angle asalready described so as to assist carrying them to the place of use ordisposal, for example directly to the whirling flame in a furnace. v

The heavy particles traveling around the periphery of the curved passageare sooner or later preferably the passage. As herein illustrated theheavy particles are carried clear around through the length of thepassage, at the end of which is a space receiving the heavy particlesand delivering them to the return pipe 16 as will be more particularlydescribed, this pipe carrying the particles back, for example to thepulverizing' machine. In order to improve the separating action it ispreferable that the velocity of flow through the curved passage shall berelatively high, to give effective centrifugal force, while the travelthrough the discharge slots or nozzles is relatively slow to prevent theforcible inward dragging of the heavy particles against theircentrifugal force. For this purpose, the cross sectional area of thepassage entrance is preferably less than the aggregate effectivedischarge area of all of the slots or nozzles 23; and as will be furtherdescribed the curved passage preferably decreases or contracts in crosssectional area throughout its length so as. to prevent an undesirabledecrease in velocity and pressure notwithstanding the disperipherallyejected from whirling flame is injected at high speed into thecombustion chamber.

charge of substantial portions through the successive apertures. a As aburner it is highly desirable to provide for thorough mixlng andinstantaneous combustion, with a turbulent flame occupying but a smallvolume. A whirling action is produced with this invention by the factthat the jets delivered into the central space through the apertures 23-depart from a radial direction, each jet being discharged at an inclineto the radius on which it enters or tangential to an imaginary cylinderabout which a whirl is thus set up. This ortex action may be obtained indifferent ways. In Figs. 1, 2 and 3 the action occurs with the use ofsimple discharge slots 23 due to the fact that 'the air and fuel beforeit is discharged through the slots is already traveling in tangentialdirections so that the jets issue from the apertures in the offsetmanner described, as .best indicated by the arrows in Fig. 2.

As already described the jets are delivered not only with the vortexaction, but they are directed toward the furnace, so that a To producethe most effective and uniform whirling vortex of delivered fuel it is Yadvantageous to provide for substantially uniform pressure and velocityin the-materials discharged through the apertures 23, or at least toarrange that the discharged velocities through the successive aperturesare maintained sufliciently high to roduce an effective whirling action.For t is purpose, as clearly shown in Figs. 1 and 2, the

, curved passage 21 is shown as progressively contracting in size orcross sectional area, thus making possible a high static pressurethroughout the extent of the passage, a high velocity therein forclassification pur oses,i and a high discharge velocity throug thesuccessive apertures. This progressive contraction of the curved passage1s preferably provided by progressive reduction of its radial dimension,as shown, while maintaining its .axial depth substantially uniform, sothat the discharge apertures 23 may be of uniform length. By thisarrangementeach of the passage end walls 26 is progressively narrowed,giving the spiral conformation as shown in Figs. 1 and 2. The dischargeapertures 23 are herein shown ascof uniform dimension both axially andtransversely, which would generally be. satisfactory.

' As already indicated the fuel and primary air receive a supply ofsecondary air within the central space 24. The primary air may beregulable at the pulverizer or otherwise by damper, and the secondaryair may be similarly regulable, so that the two may be coordinated inrelation to each other to afford a total quantity of air as.may berequired for the complete combustion of the fuel being delivered.

The secondary air may be drawn through the central space from theexterior. Coming toward-the observer in Figs. 1 and 2, and passin to theleft in Fig. 3, the secondary air wi l intersect with the jets of fuelladen air so as to give a most intimate mixing action and consequentcomplete combustion. Instead of relying upon natural draft for secondaryair it is preferred to forcibly deliver the air through the centralspace. The arrangement of the present burner is such that the secondaryair can readily be provided by a rotary fan 27 of the propeller type,which has the additional advantage that it delivers the air forwardlywith a whirling motion, which may be in the same direction as the whirlor vortex of delivered fuel, so as to accentuate the whirling motion andquick combustion. The fan 27 is shown mounted on brackets 28 withinanair box 29. The fan may be driven mechanically in any desired manner,for example by a motor 30 which may be placed within or outside of theair box 29. The

supplied to the burner may be by a damper .31 of the louver "type, orotherwise.

A preferable adjunct to the curved passage consists 'of baffling orretarding means therein for obstructing or agitating the advancingmaterials so as to create eddies and assist the thorough extraction ofthe finer particles, to be carried forward with the air, and thecentrifugal projection of the I eavier particles to the periphery. Thusin Fig. 2 is shown a system of bafiles 32 in the form of circular rodslocated at or near the periphery within the channel. The tendencfy ofthese is to cause disturbances in the orward flow of that the agitationgives the finer particles a better opportunity to be taken up in the airstream and discharged into the centralspace, the heavier particlesreturning toward the periphery following each ballie. It is not intendedto limit the shape or position of the baffles 32, and they may forexample be of angular shape spaced slightly from the peripheral wall, asindicated by the bafiies 33 in Fig. 7. It ma also be desirable toprovide strips or afiies 34 as shown in Fig. 7 along the inside wall ofthe passage, these beingplaced for example at the entering edge of eachdischarge aperture, thus tending to deflect towardthe peulverizedmaterials so ing space or Chamber preferably below the burner wall 22and adjacent to the passage entrance, the ejected heavy particlespassing from the collecting chamber into the return pipe 16 leading tothe pulverizer. According to this invention one feature of improvementis the recovery at the ejection point of a substantial percentage offine material which may have been carried around with the coarsematerial and wouldotherwise be ejected from the burner. This is hereineffected by means of an upwardly flowing air stream which serves to pickup and elevate. any descending fine particles without preventing thegravity discharge of the heavy particles. The arrangement is indicatedin Figs. 2 and 3 and in enlarged perspective in Fig. 4. The collectingchamber 35 is a generally triangular space heneath certain of thedischarge apertures 23 and enclosed between the walls 22, 25 and 26 ofthe passage, the wall 25 being extended tangentially downward from thepoint where the passage contraction ceases. The tail chamber thereforeis of the full axial depth of the burner, but, as shown in Fig. 4, itdischarges downwardly through a relatively narrow ejection passage 36communicating directly with the return pipe 16. At the .top of theejection passage 36, at each side. is a I flat wall or shelf 37, each ofthese constituting the top wall of a triangular air box 38 exterior tothe passage 36. Each of the air boxes 38 has an inward delivery opening39 to the ejection passage 36, so that the pulverized matters passingfrom the collecting chamber to the ejection passage are subjected finematerial for to the influence of the two opposite air streams comingthrough openings 39, which air effectively picks up a, large percentageof recovery and return to the burner.

The air supplied to the triangular air boxes 38 for recovery purposesmay come from any source, but preferably from the ascending entrance tothe curved passage 21. The elements 35 to 39 are shown adjacent to theinterior wall 40 of the passage entrance.

As-indicated in Fig. 4 thiswall 40 has two openings 41 leading into thetriangular air boxes 38', and for each opening isshown a damper orregulator 42, the two dampers mounted on a common rock shaft adjustableby an exterior handle 43, so that the quantity, pressure and velocity ofair ascending through the air boxes maybe properly adjusted. Theadjustment of air is to be such that there will be a constant upstream,which tends to draw only the finer particles from the ejected mass, andwhich then rises through the collecting chamber 35 carrylng the fineparticles and discharging them through the lower apertures 23 into thecentral space 24. In this way a complete, circular system of dischargeapertures is main the secondary air may flow taincd actively inoperation. In some cases the dampers 42 may be operated in cooperationwith damper 16 in the return pipe 16. Thus to throw all coal, coarse andfine, into the furnace, dampers 42 may be widely opened and damper 16closed.

Certain modifications have been described in connection with Fig. 7.Among other modifications is the arrangement shown in Fig. 5 wherein theinside wall 22 of the curved passage 21 is flaring as in Fig. 2, but inwhich in place of simple discharge slots are a system of dischargenozzles 23 which may be tubular and are preferably slanted to give boththe desired angular direction toward the furnace as well as'thetangential or vortex relation. These nozzles not only give more definitedischarge action, but have the advantage that the whirling flow of fuelladen air is surrounded by a substantially clear or free space,

namely between the nozzles, through which so that the de livered flamewill be surrounded by an envelop of secondary air. The wall 22 may becylindrical as in Fig. 8, with nozzles 23 similar to nozzles 23.

Fig. 6 shows an arrangement wherein the secondary air instead of beingdrawn or forced endwise through the central space is injected with avortex action similar to the injection of fuel. This may be accomplishedby a substantial duplicate of the curved fuel passage 21, namely betweenthe latter and the furnace. An air supply pipe 44 is shown deliveringtangentially into a progressively contracting curved passage 45, whichin turn delivers into the central space through a system of slots 46,the effect of which will be to give a whirling action to the air in thesame direction as that of the fuel, the two combining in a forcibleturbulent vortex of thoroughly mixed fuel and air. In this case the rearor outer end of the space 24 may be wholly closed by a wall 47, it beingintended that all necessary air is admitted through the two passages 21and 45; although the wall 47 might carry a regulable damper. Thisdescribed modification is of especial utility where the secondary air isto be preheated, for example in the furnace walls, the preheatingchannels delivering to the air passage 45. 7

It will thus be seen that there has been described a combined burner andclassifier embodying the principles and attaining the objects of thepresent invention. Since many matters of operation, combination,arrangement and structure may be variously modified without departingfrom the prin-' are ' coarse fuel particles,

, coarse fuel particles,

What is claimed is:

1. A burner for pulverized fuel comprising walls forming a curvedconduit, the inner wall of the conduit defining an axial passage andbeing provided with an opening establishing communication between saidconduit and passage, and the outer wall being provided with an outletopening for coarse fuel particles, means for supplying air andpulverized fuel to saidconduit at a point circumferentially remote fromsaid,

outlet opening in the direction .of travel, and walls forming acollecting chamber communicating with the outlet opening.

2. A burner forpulverized fuel comprising walls forming a curvedconduit, the inner wall of the conduit defining an axial passage andbeing providedwith an opening establishing communication between saidconduit and passage, and the outer wall being provided with an outletopening for means for supplying air and pulverized fuel to said conduitat a point circumferentially remote from said outlet opening in thedirection of travel, the conduit being shaped to provide a graduallydecreasing cross sectional area throughout its extent, and walls forminga collecting chamber communicating with the outlet opening.

3. A burner for pulverized fuel comprising walls forming an annularchamber, the inner wall OftllQ chamber defining an axial passage andbeing provided with an opening establishing communication between saidchamber and passage, and the outer wall being providedv with an outletopening for means for supplying air and pulverized fuel tangentially tosaid chamber through its outer wall,and walls forming a collectingchamber communicat ing with the outlet opening. 1

' 4. A burnerfor pulverized fuel comprising walls forming an annularchamber, the inner wall of the chamber defining an axial passage andbeing provided with an open ing establishing communication between saidchamber and passage, and the outer wall being provided with an outletopening for coarse fuel particles, means for supplying air andpulverized fuel tangentially to said chamber through its outer wall, andmeans for admitting a current of air to the chamber through said outletopening, thereby preventing ejection of fine fuel particles.

5. A burner for pulverized fuel comprising walls forming an annularchamber, the inner wall of the chamber defining an axial passage andbeing provided with spaced apertures establishing" communication betweensaid chamber and passage, and the outer wall being provided withan-outlet opening for .ticles from the coarse chamber and coarse fuelparticles, means for supplylng air and pulverized fuel tangentially tosaid chamber through its outer wall, and a set of bafiles adjacent tothe entering edges of the apertures operating to dirlelct coarse fuelparticles toward the outer wa 6. In combination -with a furnace wallhaving an opening, a burner for pulverized fuel-comprising walls forminga substantially circular chamber mounted adjacent to and substantiallycoaxial with said opening, means to introduce pulverized fuel and airinto said chamber and cause the fuel to travel along the peripheral wallof the chamber, thereby separating the coarse particles of fuel bycentrifugal force into an outer zone surrounding the fine, a passagecommunicating with the central portion of the chamber which delivers thefine particles through and an ejection passage communicating with theouter zone through which the coarse particles in the outer zone mayescape from the burner.

7. A burner as in claim 6 and wherein a damper is provided to' open orclose said ejection passage.

the opening in the furnace wall,

8. A burner for pulverized fuel comprising walls forming a substantiallycircular chamber, means for supplyingair and pulverized fuel to saidchamber in a direction tangential to the peripheral wall of the chamberand thereby causing the fuel to ticles, and walls forming a collectingcham-.

ber communicating with said last-mentioned outlet opening.

9. A burner as in claim 8 and wherein a system of bafiles is providedadjacent the inner surface of the peripheral wall to retard or agitatethe heavy material and thereby facilitate separation of the fine fuelpar particles;

10. A burner for pulverized fuel comprising walls forming asubstantially circular an axial outlet passage communicating therewith,the peripheral wall of the chamber being provided with an out letopening through which coarse fuel particles may pass and be separatedfrom the stream of fine fuel, walls enclosing a space communicating withsaid opening into whicl thecoarse particles may escape from the burner,and means for supplying pulverizedfuel and air to the chamber m adirection

